Nitrates in our drinking water may be leading to babies being born prematurely or underweight.

Pregnant women drinking water with 10 milligrams of nitrates a litre are 250 percent more likely to experience a premature birth (between 20-31 weeks), University of Otago researchers found from analysis of recent Danish and American research.

The current nitrate limit in New Zealand is 11.3mg/L - which means the levels at which these premature births occurred is within the legal limit of nitrates in New Zealand. 

This is the latest in a growing list of health concerns stemming from the level of nitrates in our drinking water.

Nitrates are a chemical compound that are most commonly used as fertilisers by the agricultural industry. The expansion of the dairy industry in New Zealand over the past thirty years has seen a 629% increase in nitrogen fertiliser use. This has led to nitrates becoming one of the most common drinking water contaminants in the country. 

The 11.3mg/L limit was set according to the level at which an immediate health impact occurs. Most commonly Blue Baby Syndrome, where infants who drink water with nitrates at this level can stop processing oxygen properly, which can lead to long-term disability or death.

But, recent research in New Zealand and abroad has identified health impacts from consuming nitrates that don’t present immediately, but result from long-term exposure - such as bowel cancer.

Another University of Otago study, released earlier this year, also estimated 138,000 New Zealanders were drinking water with nitrate levels over 5mg/L - primarily those living in rural areas.

Bowel cancer is the second highest cancer death in New Zealand, and nitrates could be a contributing factor for as many as 800,000 people.

Research has found a link between bowel cancer and nitrates in the water, at levels as low as 0.87mg/L - more than 11 times less than our current limit.

The University of Otago report concluded that this data reinforces the need for better reporting on nitrate levels in our water and the need for more research on the impact of those nitrates on our health.

“This evidence reinforces the need for a precautionary approach to setting lower nitrate limits in drinking water for human and ecological health.”

Green MP Eugenie Sage is calling for action based on the growing number of findings about the health impacts of nitrates in our drinking water.

We need the Ministry of Health and District Health Boards to do more research here in New Zealand,” Sage said.

“Given that this overseas research has shown health impacts below the current standard, if we are getting adverse health effects below that then the trigger levels in regional plans will potentially need to be looked at.”

In a post on Facebook, MP Sage added: “We need to better protect source waters and human health from nitrate pollution. That means a major reduction in synthetic fertiliser use and cow numbers.”

DairyNZ strategy and investment leader Dr David Burger said that they agree this issue demands attention. He wanted the Ministry of Health to provide urgent guidance.

“There have been numerous experts providing conflicting information around the potential impact of nitrate in water, on human health,” Dr Burger said. “We agree there is a need for further study and a comprehensive review of current research findings.”

“If we are going to review current drinking water standards, we need robust and independent information to support that and this needs to be led by the Ministry of Health.”